Impact of solar heat enhanced by the use of black polypropylene sheets on the development of Callosobruchus maculatus Fabricius (Coleoptera: Chrysomelidae) eggs and germinabilty of cowpea seeds

Abstract

Post-harvest losses caused by Callosobruchus maculatus is a major constraint to cowpea production and the improper use of synthetic insecticides by most farmers have resulted in environmental, health hazards, and development of insecticide resistance in insects. This study evaluates the efficacy of solar heat treatment using double-layered black polypropylene sheets in suppressing the development of the cowpea bruchid eggs and the effect of the heat absorbed on the germination potential of cowpea seeds. Five pairs of 2 – 3-day old adult C. maculatus were allowed to oviposit for ten days on 50 g cowpea seeds in a glass jar in the laboratory before exposure to 24, 48, 72 and 96 h solar heat treatment regimes. Infested cowpea seeds but not exposed to solarization was set along with the treatments while uninfested cowpea seeds was also set along and used as part of the germinability test. The experiment was laid out in a completely randomized design and treatments were replicated four times. The results showed that there were no significant differences among the number of eggs laid by adult C. maculatus on the cowpea seeds before solar heat treatment. Solar heat treatment of the cowpea seed at 24 h achieved 100% egg mortality of C. maculatus thus preventing adult emergence. The effect of solarization on seed viability showed that there were no significant differences between the infested cowpea seeds exposed to different solar radiation regimes when compared to uninfested cowpea seeds – range; 74% – 99% germination. The results showed that 24 h solar heat exposure of cowpea seeds in double-layered black polypropylene sheets could be the thermal death point of C. maculatus eggs on the seeds in the study area.

Management of Maize Weevil (Sitophilus zeamais) Using Hermetic and Non-Hermetic Storage Containers: A Short Communication

“…This result agreed with the findings of Demmirew et al 15 that the highest rates of maize weevil and Angoumois moth mortality were recorded when grain was exposed to the sun heat using a black polyethylene sheet. Similarly, findings of Ajayi et al 16 also suggested that solar heat exposure of Callosobruchus maculatus eggs on cow pea seeds resulted in the death of the eggs after 24 hrs at the thermal death point. In a non-hermetic containers, only 13% of the weevils have died, indicating that storage structures that allow air circulation favor weevil survival and reproduction.…”

Efficacy of Solar Heating System on Mortality, Reproduction, and Antioxidant Enzymes in Trogoderma granarium Everts and Stegobium paniceum (L.)

“…Solar disinfestation was also found to be effective in controlling bruchids in pigeon peas without negatively affecting germination (Gunewardena, 2002). It has been reported that solarization had no negative effect on the seed viability of the cowpea seeds exposed to different solar radiation when compared to the control cowpea seeds (Ajayi et al, 2021). It has also been reported that heat treatment prevents insect pests outbreak during storage conditions, and in some cases, stimulates the germination of treated seeds compared to the untreated ones (Maina and Lale, 2004;Fawki et al, 2014).…”

“…The temperature of the seeds can be increased from 52°C to 65°C when these were kept on a black polythene sheet under the sun. This method causes the death of eggs and developing stages of Callosobruchus effectively (Gbaye et al, 2011;Baoua et al, 2012a, b;Ajayi et al, 2021). Lale and Vidal (2003) reported that a heat of 40°C had a dramatic effect on adult bruchid beetles.…”

Management of stored grain pest with special reference to Callosobruchus maculatus, a major pest of cowpea: A review

“…This method causes the death eggs and developing stages of Callosobruchus effectively. Disinfestation unit can be driven with the heat of solar energy ( Gbaye et al., 2011 ; Baoua et al., 2012a , b ; Ajayi et al., 2021 ). The treatment with solar heat was found that the pest outbreak become negligible during storage conditions.…”